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Saturday, January 31, 2015

Over a course period of time, disk stop working in a computer is to be expected and if it does, then all the data is lost. Oh no, that's not good! In this article, we will take a look on mirroring the data from a disk to another disk using software, and so the data are duplicated on at least two disks. This will reduced the data loss risk by 50%! There is also hardware raid but in this article, we will look into software raid. Specifically software raid one, that is mirroring. For detail explanation of software raid one, please read on this link but for a shorter explanation, it is basically save the data into two disk at once and read from two disk.

This article assumed you have two disks with same storage capacity and only one partition per disk and this one partition occupied the whole disk size. So the operating system detected both disks as sda and sdb. Let's start to partition them first. Note, create partition will make your current data lost and make sure you backup your data somewhere else safely before continue.

root@localhost:~# fdisk /dev/sdb

Welcome to fdisk (util-linux 2.25.1).Changes will remain in memory only, until you decide to write them.Be careful before using the write command.

As you can see above, this is supposed to be the end result it should be. You can type m for help. To create a partition, this is your homework, but as a hints, you need add a new partition, with only 1 partition and used all all the cylinder. Then you need to change the disk partition type to Linux raid auto and remember to save the change you made so fdisk will write the partition and partition type to the disk.

Repeat this procedure for another disk, sdc. The partition information of sdc should be identical to sdb above. Note, you can use fdisk -l /dev/sdb and fdisk -l /dev/sdc to verify the disk is changed accordingly.

root@localhost:~# fdisk /dev/sdc

Welcome to fdisk (util-linux 2.25.1).Changes will remain in memory only, until you decide to write them.Be careful before using the write command.